A gradient magnetic field generating system used for magnetic resonance imaging has a limit of usage in terms of electrical power. One method for avoiding this is to supply a current to gradient coils such that the amount of the current supplied to the gradient magnetic field generating system becomes unquestionably lower than the limit of usage in terms of the electrical power of the gradient magnetic field generating system, thereby safely actuating the gradient magnetic field generating system.
However, if the gradient power supply device has a surplus of power supplying capacity, the image would have been imaged under more favorable conditions, for example, by increasing the number of slices in accordance with the surplus. Precisely estimating the limit of usage of the gradient magnetic field generating system in terms of the electrical power in accordance with the imaging sequence would make it possible for a magnetic resonance imaging apparatus to flow the maximum possible gradient magnetic field current within the range of the limit of usage in terms of the electrical power and to elicit the maximized performance of the gradient magnetic field generating system.